Sitagliptin, previously identified as MK-0431, is a new oral hypoglycemic (anti-diabetic drug) of the new dipeptidyl peptidase-4 (DPP-4) inhibitor class of drugs. This enzyme-inhibiting drug is to be used either alone or in combination with metformin or a thiazolidinedione for control of type 2 diabetes mellitus. The benefit of this medicine is its lower side-effects (e.g., less hypoglycemia, less weight gain) in the control of blood glucose values.